Theoretical issues of small $x$ physics

Abstract

The perturbative QCD predictions concerning deep inelastic scattering at low $x$ are summarized. The theoretical framework based on the leading log $1/x$ resummation and $k_t$ factorization theorem is described and some recent developments concerning the BFKL equation and its generalization are discussed. The QCD expectations concerning the small $x$ behaviour of the spin dependent structure function $g_1(x,Q^2)$ are briefly summarized and the importance of the double logarithmic terms which sum contributions containing the leading powers of ${\alpha }_{s}l{n}^2(1/x)$ is emphasised. The role of studying final states in deep inelastic scattering for revealing the details of the underlying dynamics at low $x$ is pointed out and some dedicated measurements, like deep inelastic scattering accompanied by an energetic jet, the measurement of the transverse energy flow etc., are briefly discussed.

17 pages, LATEX, 7 uuencoded eps figures included

References in corpus (32)

• Single and Double BFKL Pomeron Exchange and a Dipole Picture of High Energy Hard Processes
• Unitarity and the BFKL Pomeron
• High energy QCD as a completely integrable model
• High-Energy Factorization and Small-X Deep Inelastic Scattering Beyond Leading Order
• Gauge invariant effective action for high-energy processes in QCD
• Pinning down the Glue in the Proton
• Parton Distributions of the Proton
• QCD coherence in the structure function and associated distributions at small $x$
• Dijet Production at Large Rapidity Intervals
• Production of Jet Pairs at Large Relative Rapidity in Hadron-Hadron Collisions as a Probe of the Perturbative Pomeron
• Summation of Leading Logarithms at Small x
• Properties of the BFKL equation and structure function predictions for HERA
• QCD Scaling Violation at Small x
• Transverse Energy and Forward Jet Production in the Low $x$ Regime at HERA
• Scale Dependence and Small-x Behaviour of Polarized Parton Distributions
• Effective Action for Multi-Regge Processes in QCD
• PHENOMENOLOGICAL APPROACH TO UNPOLARIZED AND POLARIZED PARTON DISTRIBUTIONS AND EXPERIMENTAL TESTS
• The Spin Dependence of Diffractive Processes and Implications for the Small $x$ Behaviour of $g_1$ and the Spin Content of the Nucleon
• Radiative Parton Model Analysis of Polarized Deep Inelastic Lepton Nucleon Scattering
• Kt-Factorization vs. Renormalization Group: A small-x Consistency Argument
• THE GLUON DISTRIBUTION AT SMALL x OBTAINED FROM A UNIFIED EVOLUTION EQUATION.
• Symmetry Properties of the Effective Action for High-Energy Scattering in QCD
• How does the BFKL-Pomeron couple to quarks ?
• The small $x$ behaviour of $g_1$
• Analytic Approach to Small-X Structure Functions
• QCD Predictions for the Transverse Energy Flow in Deep-Inelastic Scattering in the Small x HERA Regime
• Dijet Production at HERA as a Probe of BFKL Dynamics
• Experimental Evidence for Simple Relations between Unpolarized and Polarized Parton Distributions
• Transverse Energy Flow at HERA
• BFKL predictions at small x from k_T and collinear factorization viewpoints
• An analytic solution of the BFKL equation with momentum cutoffs
• Physics at Low x

Cited by in corpus (4)

• Nonlinear GLR-MQ evolution equation and Q^2-evolution of gluon distribution function
• Non-equilibrium QCD: Interplay of hard and soft dynamics in high-energy multi-gluon beams
• Working Group Report on the Structure of the Proton
• Small-x analysis on the effect of gluon recombinations inside hadrons in light of the GLR-MQ-ZRS equation